This invention pertains generally to apparatus for coating materials with a vapor and more particularly to an induction heated source for vaporizing metals and other materials to be deposited in a vacuum.
Induction heated vapor sources heretofore provided for use in vacuum deposition of thin films commonly have utilized heating coils fabricated of a hollow conductor through which a coolant is circulated. The coil is energized with a radio frequency current to produce a magnetic field which induces a secondary current in the load or succeptor thus supplying heat to the material, and the amount of heat produced is dependent upon both the amount of current and the number of turns in the coil as well as the frequency of the current, nature of the material and the relative geometry of the coil and load.
With heating coils fabricated of hollow conductors, the number of turns that can be used in a given space is generally limited, and consequently a relatively high current is required to produce a given amount of heat. The higher current requires larger connecting cables and fittings, and with large currents the connecting cables are frequently water cooled hollow conductors which are difficult to install and work with.